The invention relates to a sensor for measuring electrical properties selected from a group consisting of current strength and voltage. The sensor includes a source of testing light with a particular parameter; an optical transparent medium being arranged in an electrical field, which surrounds a conductor and is produced by the electricity flowing in the conductor, the testing light being sent through the medium to experience a change in the parameter that is determined by defined optical material constants of the medium, which constants depend on the temperature of the medium and the particular field strength of the electromagnetic field; an evaluation means to obtain a quantity of the modifications of the parameter of the testing light passing through the medium so that the current strength can be determined with the aid of the quantity and the material constant.
Sensors of the named type are known and are of interest for energy measurement tasks. Sensors of this type are mostly used for measuring current strength and/or voltage of alternating current.
A problem in sensors of this type is the material constant of the optically transparent medium intended for the measurement, which constant is dependent on the temperature of this medium, by means of which constant a required measurement precision cannot be achieved.
In order to take into account this material-specific temperature dependence, it is known to arrange an external conventional temperature sensor on the medium intended for the measurement, which sensor measures the temperature of this medium immediately. The electrical current strength to be measured can then be determined with the material constant allocated to this measured temperature.